Questions tagged [rdbms]

Relational Database Management System, a widely used type of database management system characterised by its extensive use of joining as a core operational principle.

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2answers
24 views

large number of tables and postgres query performace

I have a scenario where there are 40000 tables in the database. but there are no huge unions. Very simple single table select queries are performing much slower than usual (table with just 600,000 ...
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1answer
104 views

Converting a graph database schema to a relational database schema

I currently am using a graph database and am considering moving off of it to a relational database management system like PostgreSQL. My concern is that I have lots of relationships between ...
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1answer
30 views

@OneToMany mapping but only one is needed

I have to create a new table to store version numbers of Terms&Conditions user have accepted and the time stamp of when they click accept. (This table only contains info related to user. Info ...
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1answer
36 views

How does this replication behaviour work in a RDBMS?

Consider a 3 node (N1, N2, N3) system N1 is master (used for writes) and N2, N3 (used for reads) are slaves Write request comes to update R to R1, N1 writes to disk and crashed without replication ...
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1answer
157 views

Count of range on datetime in MySql

I want to group table entries for each userId only if they are consecutive entries in the table. I have a table like this. id userId transactionTime 1 1 2016-04-13 22:15:44 2 1 ...
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1answer
53 views

Need Help in building database

I am developing an app that send messages (email and sms) to users. The db must also maintains the list of messages send to users. And also the status of messages send to user like send or failed. I ...
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1answer
56 views

Big data table processing with RDBMS like MySQL?

I have two tables Customers and Orders and each has 100 million records. Now I have to join these two tables on the column customer_id in both Customer and Order table to generate a report. ...
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1answer
17 views

Unable to create DB trace using DEA

I want to create a DB trace file using DEA(Database Experimentation Assistant). I am using below softwares: -SQL Server Express 2012 on Win10 machine where my DB is present. -DEA is installed on a ...
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1answer
45 views

How can Update table column with the virtual column?

I want to update repetitive columns, And I build virtual column for did this. I can "select" but can't "update" Here is SQL Fiddle : http://sqlfiddle.com/#!9/d09189/3 Also Code review : I have ...
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1answer
103 views

What is the point of a consistent and partition tolerant multi-master DB Architecture as opposed to Master-Slave

I should emphasize that my question is in regard to CP (Consistent and Partition Tolerant) systems. A lot of widely used NoSQL databases such as Mongo and Redis seem to fall in the CP category. And ...
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1answer
50 views

Oracle Sequential or parallel read?

From web server i initiate two separate concurrent threads/requests to read from two different DBMS(oracle) tables(employee and department). Both web server and oracle are on separate node(quad core ...
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1answer
250 views

How to store external IDs from different sources?

I have a table of customers with a PK that we can use as an identifier for our internal system. These customers may belong to different companies, each of which may have an external ID in some ...
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1answer
37 views

Which foreign keys do I use if they are repeated

I have the following two tables company_relationships |ID|Company_ID|Affiliate_ID|<Relationship Info>| +--+----------+------------+-------------------+ jobs |ID|Company_ID|<Job Info>| +...
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1answer
113 views

Oracle dataguard - Redo apply

In a low bandwidth environment when a transaction commits that generates a large amount of redo data will cause other independent transactions to slow down. This is because the redo data of small ...
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1answer
88 views

Speed up LEFT JOIN with OR operator in ON clause

I have a query that uses a LEFT JOIN with an OR operator within the ON clause. When commenting out the OR operator the query runs in ~150ms. With the OR operator kept in the query takes over 80s to ...
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1answer
10k views

Difference between assertion and trigger in PostgreSQL?

A trigger is a statement or a block of statement which are executed automatically by the system when an event like insert, update or delete takes place on a table. But I don't know where we use ...
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0answers
109 views

Understanding multivalued dependencies

This is my first time studying multivalued dependencies and there is a question that was posted by my lecturer as a class exercise. I have an answer, but I'm not 100% sure it was right. Please let me ...
2
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0answers
33 views

How to accept lock request using intent locking?

No matter how much I try, I do not understand compatibility matrix of intent locking. Why were SIX and IX denied if x lock has been held? Suppose x lock holds for record r1 then taking IX just means ...
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0answers
40 views

Coffee shop static tag/attribute querying (satisfying AND & OR condition groups) - Relational DB/DBMS or NoSQL?

Let's say you are storing information about coffee shops, and you want to assign an arbitrary number/assortment of static tags/labels to each cafe which act like attributes (i.e., the cafe either has ...
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0answers
33 views

Does two phase locking apply to individual transactions, or the schedule as a whole?

Problem I have conflicting perceptions of when a schedule violates 2PL or not. My first perception is that 2PL only applies to the level of a transaction at a time, since this is what I learned in a ...
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0answers
35 views

Equivalent of stored procedures for other database systems?

I am trying to compare centralized, distributed database systems and blockchains in several points and got stuck when searching about 'stored procedures'. So far, I have thought that this is a ...
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0answers
545 views

RDBMS sports league database

I am trying to create a database structure that will allow me to store records of league matches across multiple seasons and divisions. I have the following rules that need to be maintained: A league ...
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0answers
116 views

DBMS Query Preprocessor Checks Semantics or Syntax?

I encountered the following statement when reading about the constituents of a query processor in a DBMS: ... (b) A query preprocessor, which performs semantic checks on the query (e.g., making ...
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0answers
50 views

Logical data independence

I have a basic doubt about logical data independence. I read that in logical independence, we can remove attributes from relation without affecting external schema. How can the removal of attribute ...
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0answers
90 views

What's an example of a Distributed Database Query?

Since I may not come across or get a chance to use a distributed database system. I would like to understand an example of a Distributed Database Query. I know that in a distributed system, you have ...
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0answers
309 views

Would it be good practice to represent MongoDB ObjectId as a String or a Blob type in SQL Lite (RDMS world)?

All: We have a software application with 1) Web-based component 2) Mobile-based component Our 1) Web-based component uses a) MongoDB as the Database b) ASP.NET C# Our 2) Mobile-based component ...
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0answers
100 views

Why NOSql should be more performant than RDBMS under structured data loads?

The main reason NoSQL dbms have become so common is the need of storing unstructured data where a Relational database instead would require carefully designing a database schema and fitting data into ...
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0answers
11 views

Understanding connection between different database concurrency control protocols

I have came across following diagram related to timestamp based concurrency control protocols in database systems (as summarized in these sldes or detailed in the book by Korth et al.): I don't know ...